Dynamic adjustment of localized constraints

Abstract

Distributed integrity constraints are costly to check; they may also conflict with site autonomy for multidatabases. It has been shown that simple distributed linear inequality constraints can be broken up into independent local constraints that can be dynamically adjusted. Earlier, we have given a framework for generalizing this approach and shown that more complex constraints can be handled on its basis. In this paper, we focus on dynamic adjustment of the local constraints. Special care is needed for constraints that are more complex than linear inequalities since simultaneous requests for constraint adjustment can lead to inconsistency. We have explored various issues including the problem of simultaneity, and have tested our solutions using an implementation. Our experimental results show that simultaneity is important, that our solutions are effective, and the overall strategy of localization is successful.